I think it depends on how big the rider is. If you are thin enough you could probably jump off the roof on to the saddle and ride off. If you big like me I think the a stride method makes more since.
We used to get a running start and jump on in the good old days of the 60's. Most of the time we would put the left foot on the peddle and start pushing with the right foot until we got up some speed and then swing our right leg across the frame. Hi Ho Silver!!
They were good old days.
Joe